WeakHashSet.java

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package org.jruby.util.collections;

import java.util.*;

/**
 * A simple set that uses weak references to ensure that its elements can be garbage collected.
 * See WeakHashMap.
 *
 * @author <a href="http://www.cs.auckland.ac.nz/~robert/">Robert Egglestone</a>
 */
public class WeakHashSet<T> implements Set<T> {
    private WeakHashMap<T,Object> map;

    public WeakHashSet() {
        map = new WeakHashMap<T,Object>();
    }

    public WeakHashSet(int size) {
        map = new WeakHashMap<T,Object>(size);
    }

    public boolean add(T o) {
        Object previousValue = map.put(o, null);
        return previousValue == null;
    }

    public Iterator<T> iterator() {
        return map.keySet().iterator();
    }

    public int size() {
        return map.size();
    }

    public boolean isEmpty() {
        return map.isEmpty();
    }

    public boolean contains(Object o) {
        return map.containsKey(o);
    }

    public boolean remove(Object o) {
        boolean contains = contains(o);
        map.remove(o);
        return contains;
    }

    public boolean removeAll(Collection collection) {
        return map.keySet().removeAll(collection);
    }

    public boolean retainAll(Collection collection) {
        return map.keySet().retainAll(collection);
    }

    public void clear() {
        map.clear();
    }

    public Object[] toArray() {
        return map.keySet().toArray();
    }

    public boolean containsAll(Collection arg0) {
        return map.keySet().containsAll(arg0);
    }

    public boolean addAll(Collection<? extends T> arg0) {
        boolean added = false;
        for (T i: arg0) {
            add(i);
            added = true;
        }
        return added;
    }

    public <T> T[] toArray(T[] arg0) {
        return map.keySet().toArray(arg0);
    }

}